构建可增强荧光检测灵敏度的表面掺铕钒酸钆及其形成机理研究

Europium ions doped vanadate gadolinium nanophosphor is one of the most promising luminescence probes. It is difficult to enhance the detection sensitivity via increasing the original luminescence intensity. So this project constructs a new vanadate gadolinium nanoparticle doped with europium ions on its surface. Its original luminescence intensity is high due to the surface modification of protective ligand. However, the pretty low testing luminescence intensity results from the fact that the europium ions on the surface are quenched after the desorption of the ligands. Thus, the detection sensitivity of the new nanoparticles is expected to be enhanced. In the first part of this project, a thin film of graphene oxide is adopted to absorb the europium ions. Then the thermodynamic parameters of nucleation and growth of vanadate gadolinium are controlled to restrict the europium ion locating on the interface between vanadate gadolinium and graphene oxide. An analysis model about forces on the europium ion is established as well as the boundary conditions of its diffusing behaviour. Consequently, the formation mechanism of the vanadate gadolinium surface-doped with europium ions is demonstrated. Secondly, the relationship between structural features of the ligands and the luminescent intensity is discussed to propose the structural criterion of luminescent protective capability and the optimal best ligand is determined. In the final part, the as-obtained luminescence probe is applied to detect copper ions and the sensitivity enhancement mechanism is demonstrated. This project is expected to solve the key problem about controlling europium ions on the surface of vanadate gadolinium. The substantial reduce of the testing luminescence intensity is available. This project introduces a new approach to enhance the detection sensitivity.

掺铕钒酸钆纳米发光材料是超灵敏荧光检测领域极具潜力的荧光探针材料。单纯采用提高初始荧光强度以增强荧光检测灵敏度的研究已达瓶颈。因此，本项目设计了控制铕离子掺杂在钒酸钆表面的新型结构，利用配位体表面修饰维持初始荧光强度较高，检测时配位体脱附，表面铕离子发生荧光猝灭，导致检出荧光强度大幅下降，从而增强荧光检测灵敏度。首先，采用氧化石墨烯薄膜吸附铕离子，再控制钒酸钆形核长大的热力学驱动力和动力学参量，使铕离子在氧化石墨烯与钒酸钆晶体之间保持平衡，建立铕离子的受力分析模型和扩散边界条件，阐明表面掺铕钒酸钆的形成机理。其次，研究配位体的结构特征对初始荧光强度的影响，提出荧光保护能力的结构判据并确定最优配位体。最后，应用新型结构荧光探针检测铜离子，揭示表面掺杂结构对荧光检测灵敏度的增强机制。研究成果有望解决将发光中心掺杂在基体表面的关键问题，实现检出荧光强度的大幅降低，为提高荧光检测灵敏度提供新思路。

稀土纳米发光材料是超灵敏荧光检测领域极具潜力的荧光探针材料。然而由于受到浓度猝灭和表面猝灭效应的限制，荧光强度提升困难，且单纯采用提高初始荧光强度以增强荧光检测灵敏度的研究已达瓶颈。因此，本项目设计了多种结构稀土纳米发光材料以提高荧光检测灵敏度。首先，通过三种碱金属离子共掺杂GdVO4:Eu3+，提供电荷补偿剂并引发晶格畸变的方式提高稀土离子浓度猝灭阈值，建立晶体结构与浓度猝灭效应的调控模型，阐明浓度猝灭抑制机理；其次，对NaGdF4:Yb, Tm上转换纳米发光材料进行掺杂浓度优化和同质（NaGdF4:Yb）、异质（SiO2）壳层包覆，有效缓解了表面猝灭效应，研究配位体和壳层结构特征对初始荧光强度的影响，提出荧光保护能力的结构判据；最后，采用氧化石墨烯薄膜吸附铕离子，再控制钒酸钆形核长大的热力学驱动力和动力学参量，使铕离子在氧化石墨烯与钒酸钆晶体之间保持平衡，建立铕离子的受力分析模型和扩散边界条件，阐明表面掺铕钒酸钆的形成机理。研究成果有望解决将发光中心掺杂在基体表面的关键问题，实现检出荧光强度的大幅降低，为提高荧光检测灵敏度提供新思路。